To join the ProAudio Seed program at Apple, you can simply send me (Markus Fritze mfritze@apple.com) an email with your name, company, your (main) Audio Unit(s). Most important: I need the email matching the one used for the AppleID on your developer account, because you need an active developer account to be part of the seed program. Within a week you should send receive an invite. If not, then there is probably a spam filter on your side filtering our the invite – we had cases where this was simply not solvable, because all invites were eating by some spam filter.
That’s it,
Markus